ConsoleAppender.java

/*
 * Licensed to Elastic Search and Shay Banon under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership. Elastic Search licenses this
 * file to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *    http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied.  See the License for the
 * specific language governing permissions and limitations
 * under the License.
 */

package org.langke.util.logging.log4j;

import java.io.IOException;
import java.io.OutputStream;

import org.apache.log4j.Layout;
import org.apache.log4j.WriterAppender;
import org.apache.log4j.helpers.LogLog;
import org.langke.util.logging.Loggers;


/**
 * ConsoleAppender appends log events to <code>System.out</code> or
 * <code>System.err</code> using a layout specified by the user. The default
 * target is <code>System.out</code>.
 * <p/>
 * <p>
 * ElasticSearch: Adapter from log4j to allow to disable console logging...
 * </p>
 * 
 * @author Ceki Gülcü
 * @author Curt Arnold
 * @since 1.1
 */
public class ConsoleAppender extends WriterAppender {

	public static final String SYSTEM_OUT = "System.out";
	public static final String SYSTEM_ERR = "System.err";

	protected String target = SYSTEM_OUT;

	/**
	 * Determines if the appender honors reassignments of System.out or
	 * System.err made after configuration.
	 */
	private boolean follow = true;

	/**
	 * Constructs an unconfigured appender.
	 */
	public ConsoleAppender() {
	}

	/**
	 * Creates a configured appender.
	 * 
	 * @param layout
	 *            layout, may not be null.
	 */
	public ConsoleAppender(Layout layout) {
		this(layout, SYSTEM_OUT);
	}

	/**
	 * Creates a configured appender.
	 * 
	 * @param layout
	 *            layout, may not be null.
	 * @param target
	 *            target, either "System.err" or "System.out".
	 */
	public ConsoleAppender(Layout layout, String target) {
		setLayout(layout);
		setTarget(target);
		activateOptions();
	}

	/**
	 * Sets the value of the <b>Target</b> option. Recognized values are
	 * "System.out" and "System.err". Any other value will be ignored.
	 */
	public void setTarget(String value) {
		String v = value.trim();

		if (SYSTEM_OUT.equalsIgnoreCase(v)) {
			target = SYSTEM_OUT;
		} else if (SYSTEM_ERR.equalsIgnoreCase(v)) {
			target = SYSTEM_ERR;
		} else {
			targetWarn(value);
		}
	}

	/**
	 * Returns the current value of the <b>Target</b> property. The default
	 * value of the option is "System.out".
	 * <p/>
	 * See also {@link #setTarget}.
	 */
	public String getTarget() {
		return target;
	}

	/**
	 * Sets whether the appender honors reassignments of System.out or
	 * System.err made after configuration.
	 * 
	 * @param newValue
	 *            if true, appender will use value of System.out or System.err
	 *            in force at the time when logging events are appended.
	 * @since 1.2.13
	 */
	public final void setFollow(final boolean newValue) {
		follow = newValue;
	}

	/**
	 * Gets whether the appender honors reassignments of System.out or
	 * System.err made after configuration.
	 * 
	 * @return true if appender will use value of System.out or System.err in
	 *         force at the time when logging events are appended.
	 * @since 1.2.13
	 */
	public final boolean getFollow() {
		return follow;
	}

	void targetWarn(String val) {
		LogLog.warn("[" + val + "] should be System.out or System.err.");
		LogLog.warn("Using previously set target, System.out by default.");
	}

	/**
	 * Prepares the appender for use.
	 */
	public void activateOptions() {
		if (follow) {
			if (target.equals(SYSTEM_ERR)) {
				setWriter(createWriter(new SystemErrStream()));
			} else {
				setWriter(createWriter(new SystemOutStream()));
			}
		} else {
			if (target.equals(SYSTEM_ERR)) {
				setWriter(createWriter(System.err));
			} else {
				setWriter(createWriter(System.out));
			}
		}

		super.activateOptions();
	}

	/**
	 * {@inheritDoc}
	 */
	protected final void closeWriter() {
		if (follow) {
			super.closeWriter();
		}
	}

	/**
	 * An implementation of OutputStream that redirects to the current
	 * System.err.
	 */
	private static class SystemErrStream extends OutputStream {
		public SystemErrStream() {
		}

		public void close() {
		}

		public void flush() {
			System.err.flush();
		}

		public void write(final byte[] b) throws IOException {
			if (!Loggers.consoleLoggingEnabled()) {
				return;
			}
			System.err.write(b);
		}

		public void write(final byte[] b, final int off, final int len)
				throws IOException {
			if (!Loggers.consoleLoggingEnabled()) {
				return;
			}
			System.err.write(b, off, len);
		}

		public void write(final int b) throws IOException {
			if (!Loggers.consoleLoggingEnabled()) {
				return;
			}
			System.err.write(b);
		}
	}

	/**
	 * An implementation of OutputStream that redirects to the current
	 * System.out.
	 */
	private static class SystemOutStream extends OutputStream {
		public SystemOutStream() {
		}

		public void close() {
		}

		public void flush() {
			System.out.flush();
		}

		public void write(final byte[] b) throws IOException {
			if (!Loggers.consoleLoggingEnabled()) {
				return;
			}
			System.out.write(b);
		}

		public void write(final byte[] b, final int off, final int len)
				throws IOException {
			if (!Loggers.consoleLoggingEnabled()) {
				return;
			}
			System.out.write(b, off, len);
		}

		public void write(final int b) throws IOException {
			if (!Loggers.consoleLoggingEnabled()) {
				return;
			}
			System.out.write(b);
		}
	}

}